At the beginning of chapter 24, Miss Bingley sends Jane a letter. While we do not get to read the letter, its contents are summarized for us: Instead of communicating any intention on Bingley's part to propose to Jane, Miss Bingley describes the growing intimacy between the Darcys and the Bingleys. Miss Bingley praises Miss Darcy and is delighted that Mr. Bingley is staying at the Darcy house in London. It looks as if the match Miss Bingley hopes for between her brother and Miss Darcy is steadily moving forward.
Elizabeth reacts to this news with silent anger ("indignation" is the word Austen uses). She can't stop dwelling on it: "She could think of nothing else." She believes Bingley still has affection for Jane, doesn't believe Bingley cares at all about Miss Darcy, and feels angry at Bingley for what she sees as his weakness of character. To her mind, Bingley has allowed his friends to influence him against his heart and his own best interests. As she puts it to herself, Bingley had been made "the slave of designing friends" and has "sacrifice[d] his own happiness" to them. She starts to despise his ease and flexibility.
Jane is so upset by the letter that she can't talk about it for a "day or two." When she does confide in Elizabeth, she exhibits a poise and equanimity that contrasts with Elizabeth's anger. She insists she will soon get over her feelings for Mr. Bingley, saying: "He shall be forgot, and we shall all be as we were before." Jane tells Elizabeth not to blame anyone for what happened.
Elizabeth is astonished at Jane's response and calls her "angelic." When Jane protests, Elizabeth says she is determined to think her "perfect."
Their different reactions to this painful letter throw into relief the different personalities of the two sisters: Elizabeth is impulsive, quick to anger, and emotional while Jane has greater self-control, is more generous about people, and has more ability to take a longer view of events.
This letter also sets up a dynamic that allows us to better understand Elizabeth's fury when she finds out that Darcy separated Jane and Bingley.